VT1536A
Isolated Digital Input/Output
Signal Conditioning Plug-on
User’s and SCPI Programming Manual
Where to Find it - Online and Printed Information:
System installation (hardware/software) ............VXIbus Configuration Guide*
HP VIC (VXI installation software)*
Module configuration and wiring .......................This Manual
SCPI programming .............................................This Manual
VXIplug&play programming ............................VXIplug&play Online Help
VXIplug&play example programs .....................VXIplug&play Online Help
VXIplug&play function reference......................VXIplug&play Online Help
Soft Front Panel information ..............................VXIplug&play Online Help
VISA language information................................Agilent/HP VISA User's Guide
Agilent/HP VEE programming information.......Agilent/HP VEE User's Manual
*Supplied with HP Command Modules , Embedded Controllers, and VXLink.
Copyright © VXI Technology, Inc., 2003
Manual Part Number: 82-0092-000
Printed in U.S.A.
VT1536A Isolated Digital
Input/Output SCP
Introduction
The VT1536A is an eight-channel Isolated Digital I/O SCP. Channels are
switch configurable as either input or output on a channel-by-channel basis.
Input-configured channels provide:
• Optically coupled isolation
• Individual switch selectable threshold levels of 5, 12, 24 and 48 VDC
• Two programmable debounce timers (150 µs to 2.4 s); one for the
SCP's lower 4 channels and one for the SCP's higher 4 channels.
• Programmable polarity
Output-configured channels provide:
• SPST Solid-state relay output
• 200 mA current carrying capability
• Relays protected by active voltage clamping
• Programmable polarity
About this Manual
This manual shows you how to configure the Signal Conditioning Plug-on
(SCP) using SCPI commands and explains the capabilities of this SCP.
The contents of this manual are:
• Identifying the Plug-on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
• Setting Configuration Switches . . . . . . . . . . . . . . . . . . . . . . . .
• Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
• Connecting To The Terminal Module . . . . . . . . . . . . . . . . . . . .
• Recommended Signal Connections . . . . . . . . . . . . . . . . . . . . .
• Input and Output Characteristics. . . . . . . . . . . . . . . . . . . . . . . .
•
•
•
•
page 4
page 4
page 5
page 5
page 6
page 7
Output Voltage Clamp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 8
Programming With SCPI Commands . . . . . . . . . . . . . . . . . . . page 10
Configuring Input Channel Polarity . . . . . . . . . . . . . . . . . . . page 11
Setting Debounce Time. . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 11
Configuring Output Channel Polarity . . . . . . . . . . . . . . . . . page 13
Programming with the VT1415A/19A Algorithm Language . page 14
*RST and *TST? (Important!) . . . . . . . . . . . . . . . . . . . . . . . . page 14
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 15
VT1536A Isolated Digital Input/Output SCP
3
Identifying the Plug-on
You'll find the VXI Technology part number on the connector side of the
SCP. For the VT1536A, the part number is: VT1536A.
Setting Configuration Switches
Each channel has a four-switch package that configure its input threshold
voltage level and I/O direction.
Locating switches
Figure 1 shows the location of each channel's configuration switch package.
Figure 1 Locating and Setting Threshold Switches
Important!
Make certain that you slide the switch handles completely to the ON or OFF
position! Verify switch settings with the INP:THReshold:LEVel? command.
An invalid switch setting will cause the related channel to behave as an input
with unknown threshold level.
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VT1536A Isolated Digital Input/Output SCP
Configuring for Input
Refer again to Figure 1 for the four valid input threshold, switch
configurations. Table 1 shows the "input zero" and "input one" levels for the
nominal threshold settings.
Table 1 Input Threshold Voltage Levels
Configuring for Output
Nominal
Threshold Level
Input One
VDC Minimum
Input Zero
VDC Maximum
5
2.1
1.4
12
7
2
24
13
3
48
25
5
By turning all four of its threshold-setting switches OFF, a channel is
configured as an output channel.
Installation
After the switches have been configured, the installation for this Plug-on is
common to several others and is covered in Chapter 1 of your VXI Module
User's Manual.
Connecting To The Terminal Module
To get started on field wiring to the VT1536A SCP you'll need to know that
input-configured channels ARE POLARIZED. That is the H terminal must
be driven positive relative to the L terminal. Output-configured channels are
not polarized. For more information see “Input and Output Characteristics”
on page 7.
The SCP connections for the Terminal Modules are shown on the
self-adhesive labels that come with the SCP. Use these to label terminal
definitions on your terminal module. The connections are shown in Figure 2.
VT1536A Isolated Digital Input/Output SCP
5
Figure 2 VT1415A/19A/22A Terminal Module Connections
Recommended Signal Connections
Figure 3 shows the recommended method of wiring isolated digital I/O
channels, as well as the maximum voltage limitations for the VT1536A.
Figure 3 shows the shields connected directly to the VT1415A/19A ground.
This is to limit potential noise on the isolated digital wiring from affecting
low-level analog channel wiring within the Terminal Module.
Note
6
The VT1536A is a true isolated SCP. There is no electrical connection
between each channel's Hi/Lo terminals and VT1415A/19A's chassis
ground. However the G (analog guard) terminals are connected through
10 kOhm resistors to chassis ground within the VT1415A/19A. These
terminals are NOT isolated.
VT1536A Isolated Digital Input/Output SCP
Figure 3 Recommended Connections and Voltage Limits
Input and Output Characteristics
This section describes the electrical characteristics of the SCP's input and
output sections, as well as the operation of the input debounce timers. Figure
4 shows a simplified schematic of one VT1536A channel.
Input Characteristics
The input section drives an opto-isolator through a resistor threshold setting
network. Your system must provide at least 1 mA of current to drive the
opto-isolator. The threshold setting network controls this drive current for
various input voltages ranging from 5 to 48 Volts (see Table 1 on page 5).
Your input voltage must be polarized positive to the Hnn terminal, and
negative to the Lnn terminal.
Output Characteristics
The opto-isolated output provides a Solid-State relay and relay protection
voltage clamping diode. The solid state relay is non-polarized. The voltage
clamping diode limits voltage at the relay output to 80 VPEAK (begins to
conduct at about 60 VPEAK). The SS relay's on-resistance is 10 Ω,
off-resistance is at least 1010Ω. The relay's turn-on time is 3 milliseconds.
VT1536A Isolated Digital Input/Output SCP
7
Figure 4 The VT1536A Input and Output Sections
Output Voltage Clamp
The output section incorporates a "crowbar" protection type voltage
clamping diode. In normal operation with the relay voltage at or below
56 Volts peak, the diode has virtually no effect (other than about
10 nanoamperes of leakage current). At 60 Volts, the diode starts to conduct
to limit further voltage excursions. In this region, the diode effectively
clamps momentary voltage spikes from inductive loads. If an overvoltage
condition occurs that drives a voltage surge in the diode to 80 Volts, the
diode will latch-on, clamping the voltage to a few volts. This latched-on
condition will continue until the current surge through the diode is reduced
to less than 150 mA, whereupon the diode returns to its off state.
Debounce Function
Setting the appropriate debounce period ensures that the VT1415A/19A
algorithm reads only the most current VALID digital input state as latched
into the SCP channel. By "valid" we mean that the signal has not made any
0-to-1 or 1-to-0 transitions for the duration of the debounce period (the
signal has settled). If the algorithm reads a channel that has not yet settled,
it will receive the previously latched valid state (no change).
Debounce is controlled using VT1415A/19A SCPI commands. When the
debounce feature is enabled, inputs are tested for debounce, and valid states
are latched every 1 1⁄ 3 debounce periods. This debounce-and-latch rate is
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VT1536A Isolated Digital Input/Output SCP
completely asynchronous with the VT1415A/19A algorithm execution rate
as set by the Trigger Timer (TRIG:TIMER command). Long debounce
periods combined with fast Trigger Timer settings would have the algorithm
executing several times for each input debounce-and-latch period.
Conversely, short debounce periods and slow Trigger Timer rates would
allow multiple debounce-and-latches per algorithm execution.
Debounce Example
Figure 5 demonstrates the use of debounce. Here we show a system that uses
a digital line to sense a switch an operator would throw to signal the
algorithm to shut down a process. The digital line runs through an electrical
environment that could cause a false shut-down signal when a large motor
starts. The motor start period is at most 0.5 seconds. The algorithm executes
every 100 ms so without debounce it could sense this electrical noise as a
false shut-down signal. If we set the debounce period to 1.228 seconds, the
VT1536A will ignore the motor start-up noise and will only latch signal
states that last as long or longer than the debounce period.
Figure 5 Example Using Debounce Feature
Data Latency
With the debounce feature on, the data latency (the time from valid signal
transition to acquisition by the algorithm is up to 1.333 times the debounce
period plus one VT1415A/19A trigger repetition period
(TRIG:TIM:PERIOD).
With the debounce feature off (INPut:DEBounce 0,(@<ch_list>), the
latency is only the algorithm repetition rate.
VT1536A Isolated Digital Input/Output SCP
9
Programming With SCPI Commands
The SCPI commands shown here query the SCP's identification string, and
perform VT1536A channel configuration. The VT1415A/19A doesn't
provide SCPI commands to read an input channel or control an output
channel. Read and write operations are performed by the VT1415A/19A's
Algorithm language. See the following section for a digital input/output
example.
*RST & Power-up
Conditions
The default configuration of the VT1536A at power-up or after a *RST
command is:
•
Channel I/O direction is as set by the threshold/direction switches
(See “Setting Configuration Switches” on page 4.).
•
Input and output channel polarity will be NORMal. This means:
-- For inputs; when the input opto isolator is being driven (is "on"), an
algorithm will read a logic 1. When the opto is off, the algorithm
reads a zero.
-- For outputs; when an algorithm writes a 1, the output relay will turn
on ("close"). Writing a zero will turn the relay off.
Remember, polarity NORMal means "1 = ON".
• Output configured channels will have their relays turned off ("open").
Checking the ID
of the SCP
To verify the SCP type(s) installed on your VXI module, use the
SYSTem:CTYPE? (@<channel>) command.
• The channel parameter specifies a single channel in the channel range
covered by the SCP of interest. The first channel number for each of
the eight SCP positions are; 0,8,16,24,32,40,48, and 56.
The value returned for the VT1536A SCP is:
HEWLETT-PACKARD,E1536A Isolated Digital I/O SCP,0,0
To determine the type of SCP installed on channels 0 through 7 send
SYST:CTYPE? (@100)
enter statement here
Determining Input
Threshold Level and
I/O Direction
The input threshold level and I/O direction is set (for each individual
channel) by hardware switches (See “Setting Configuration Switches” on
page 4.). To determine how a channel is currently configured, use the
command:
INPut:THReshold:LEVel? (@<channel>)
• Channel must specify a single channel
10
query SCP type @ ch 0
enter response string
VT1536A Isolated Digital Input/Output SCP
• INP:THR:LEV? returns a numeric value which is one of 5, 12, 24, 48 or
0 (zero) where zero means that the channel is configured as an output
and non-zero values indicate the input threshold in volts.
Note
If an invalid switch combination is set, INP:THR:LEV? will NOT return a
value and will generate the error 3105 "Invalid SCP switch setting". This
error will also be generated when *RST is executed. Channels associated
with this error will behave as input channels with unknown threshold levels.
To query the threshold level on the second channel at SCP position 2 send:
INP:THR:LEV? (@117)
enter statement here
Configuring Input
Channel Polarity
query 2nd chan on SCP pos. 2
returns 0 | 5 | 12 | 24 | 48
To configure input channel polarity use the command:
INPut:POLarity INVerted | NORMal,(@<ch_list>)
To configure the first 2 channels on an VT1536A in SCP position 4 to input
Normal polarity (opto on=logical 1) and its next 2 channels to input inverted
polarity (opto off=logical 1)send:
INP:POL NORM,(@132,133)
INP:POL INV,(@134,135)
NORM is *RST default
There is also the query form; INPut:POLarity? (@<channel>), where
<channel> must specify a single channel. INP:POL? returns NORM | INV.
Note
Setting Debounce Time
The INPut:POL command will generate the error 3107, "Channel data
direction conflicts with command" if any channel in <ch_list> is configured
as an output.
For a description of the debounce function See “Debounce Function” on
page 8. The VT1536A has two debounce timers. One for the lower four
channels, and one for the upper four channels. To set the debounce timers
use the command:
INPut:DEBounce:TIME <time>,(@<ch_list>)
• <time> can be one of 16 possible numeric values or MIN and MAX:
Note
Because the clock that generates the debounce period is asynchronous to
your input signal, there is a region of uncertainty relative to the nominal
debounce period selected. This is reflected in the “Minimum” and
“Maximum” debounce period columns in Table 2.
VT1536A Isolated Digital Input/Output SCP
11
Choose a value from the “Minimum Period” column in Table 2 that is
longer than your input signal’s undesired transition period when you
want to exclude these short term input signal transitions.
Choose a value from the “Maximum Period” column in Table 2 that is
shorter than your input signal’s expected transition period when you
want to be certain to include these desired input signal transitions.
The values to send to the VT1536A are in the “Nominal” column in
Table 2 below.
Table 2 Nominal Debounce Period and Uncertainties
Minimum Period
Nominal Value
Maximum Period
debounce off
0
debounce off
0.08 ms
0.15 ms
0.18 ms
0.20 ms
0.30 ms
0.35 ms
0.45 ms
0.60 ms
0.65 ms
0.95 ms
1.20 ms
1.30 ms
1.90 ms
2.40 ms
2.50 ms
4.10 ms
4.80 ms
5.00 ms
8.20 ms
9.60 ms
9.85 ms
16.4 ms
19.2 ms
19.7 ms
32.8 ms
38.4 ms
39.4 ms
65.5 ms
76.6 ms
78.7 ms
131 ms
153.6 ms
158 ms
262 ms
307.2 ms
315 ms
525 ms
614.4 ms
630 ms
1.05 s
1.2288 s
1.26 s
2.10 s
2.4576 s
2.52 s
-- Sending 0 or MIN turns debounce off. Sending MAX selects 2.458
seconds.
-- If a value is sent that is slightly greater than one of these values, the
next higher value (or MAX) is selected. Values outside of the range
0 - 2.4576 will generate the error -222, "Data out of range".
• <ch_list> must contain all 4 of the upper-bank channels, or all 4 of the
lower-bank channels, or all 8 channels for a given SCP. This is because
the VT1536A has two debounce timers, one for its lower 4 channels
and one for its upper 4 channels.
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VT1536A Isolated Digital Input/Output SCP
Note
The INP:DEB:TIME generate the error 3108, "E1536 debounce - each
referenced 4 Ch bank must contain at least one input". This error indicates
that you tried to set a debounce time for a bank of channels that contains no
input configured channel.
To set the debounce period to 153.6 ms for the lower 4 channels on an
VT1536A in SCP position 0 send:
INP:DEB 0.1536,(@100:103)
To set the debounce period to 1.229 seconds for the upper 4 channels on an
VT1536A in SCP position 3 send:
INP:DEB 1.229,(@128:131)
There is also the query form;
INPut:DEBounce:TIME? (@<channel>)
where <channel> must specify a single channel. INP:DEB:TIME? returns
the currently set debounce period.
Configuring Output
Channel Polarity
To configure output channel polarity use the command:
OUTPut:POLarity INVerted | NORMal,(@<ch_list>)
To configure the fifth and sixth channels on an VT1536A in SCP position 4
to output normal polarity (logical 1=relay on) and its next 2 channels to
output inverted polarity (logical 1=relay off) send:
OUTP:POL NORM,(@136,137)
OUTP:POL INV,(@138,139)
NORM is *RST default
There is also the query form; OUTPut:POLarity? (@<channel>), where
<channel> must specify a single channel. OUTP:POL? returns "NORM" or
"INV".
Notes
1. The OUTPut:POL command will generate the error 3107, "Channel
data direction conflicts with command" if any channel in <ch_list> is
configured as an input.
2. An output channel's SS relay will not change from the *RST state
(open) regardless of its POLarity setting, until an algorithm writes a
value to that channel.
VT1536A Isolated Digital Input/Output SCP
13
Programming with the VT1415A/19A Algorithm Language
The following example shows the command sequence (platform/language
independent) to transfer the digital states from the lower 4 channels (inputs)
to the upper 4 channels (outputs). In other words, the state you input to one
of the lower 4 channels will drive the corresponding output channel. The
example assumes that the SCP is installed in SCP position 0
(covers channels 0 through 7), the first four channels are configured as
inputs, and the last four are configured as outputs (See “Setting
Configuration Switches” on page 4.).
*RST
reset module to default states
ALG:DEF 'ALG1','O104=I100; O105=I101; O106=I102; O107=I103;'defines the algorithm
INIT
start algorithm (using default trig sys setup)
When the algorithm is run, digital states input to channels 0 through 3 will
be output on channels 4 through 7.
*RST and *TST? (Important!)
The *RST/Power-up state and *TST? command reset the VT1415A/19A to
its default state. This will cause all output-configured channel solid-state
relays to "open" (turn off), disable debounce, and restore channel polarity to
normal. Keep this in mind when applying the VT1536A SCP to your system
and design the "open" state as the safe state for your system.
Note
*RST will report error 3105, "Invalid SCP switch setting" if one or more
configuration switches are set to invalid configurations.
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VT1536A Isolated Digital Input/Output SCP
Specifications
SCP Power Supply Requirements
+5 Vmax
+24 Vtyp
0.072
Output Characteristics
+24 Vmax
-24 Vtype
not used
-24 Vmax
not used
Characteristic
Specification
Maximum Continuous
Voltage
56 VDC (39 VRMS)
Peak Current Load
200 mA
Relay On Resistance
10 Ω
Turn On/Off Time
3 ms
Clamping Voltage*
60 V
(see also Figure 4)
* See “Output Voltage Clamp” on page 8.
Input Characteristics
Characteristic
Specification
Maximum Continuous
Voltage
56 VDC (39 VRMS)
Maximum Input Zero
See Table 1 on page 5
Minimum Input One
See Table 1 on page 5
Input Debounce Time
150 µs - 2.4 s. See Table 2 on page 12
(see also Figure 4)
VT1536A Isolated Digital Input/Output SCP
15
Notes:
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VT1536A Isolated Digital Input/Output SCP